Corn has a high demand for water, and consistent moisture is the most important factor for high yields. A corn plant requires 20 to 30 inches of water over its growing season, depending on the variety and local conditions. Watering frequency changes dramatically as the plant progresses from a seedling to a mature crop. Aligning water delivery with the plant’s life cycle ensures maximum productivity.
Water Requirements During Corn’s Growth Stages
Water needs are relatively low during the early growth period, until about the V8 stage (eight visible leaf collars). During this time, the focus is on encouraging deep root establishment, and the plant primarily relies on moisture stored deep in the soil profile. Applying irrigation too early can lead to shallow rooting, which makes the plant more susceptible to drought later in the season.
The vegetative growth phase, from V8 up to tasseling, sees a rapid increase in water consumption as the plant develops its large leaf area. Water use during this period can reach approximately 1 inch per week, as the plant begins to transpire significant amounts of water. Although the plant is somewhat tolerant of brief water deficits during this stage, consistent moisture supports the development of maximum kernel rows on the ear.
The most sensitive and water-intensive period is the reproductive stage, which includes tasseling, silking, and early kernel fill. Water use peaks during this time, often exceeding 0.35 inches per day, or up to 2 inches per week under high-demand conditions. Water stress during silking is particularly damaging, as it can cause the silks and pollen grains to desiccate, leading directly to poor pollination and missing kernels on the ear. Supplying adequate moisture from one week before to three weeks after tasseling is necessary for top yields.
Water requirements steadily decline once the kernels reach the dough and dent stages. Continued moisture is still necessary to complete kernel development until the black layer (physiological maturity). This final stage determines final kernel weight. Allowing the soil to dry excessively during this final grain-filling period can result in lightweight kernels, even if the earlier stages received sufficient water.
Determining Water Quantity and Soil Moisture
Watering frequency should be determined by water loss from the soil, not a rigid calendar schedule. The goal is to deliver enough water to penetrate the root zone deeply, which encourages the plant to develop a robust root system. Deep, less frequent watering is generally more beneficial than shallow, daily applications that only wet the soil surface.
A simple rain gauge can verify the quantity of water delivered by irrigation or rainfall. For sprinkler systems, placing small containers in the watering area helps determine how long the system must run to deliver the target amount. For high-demand periods, ensuring the irrigation system can deliver up to 2 inches per week is necessary to meet peak evapotranspiration rates.
The most practical method for deciding when to water is the “finger test” or using a soil probe. The soil should be checked at a depth of 4 to 6 inches, where the majority of the active roots are drawing water. If the soil at this depth feels dry and crumbly, watering is necessary. Conversely, if the soil feels cool and moist, water application should be delayed.
Environmental Factors Affecting Watering Decisions
Environmental conditions require adjusting the watering schedule to account for changes in water loss through evapotranspiration (ET). High air temperatures, strong winds, and low humidity all increase the evaporative demand on the plant, causing daily ET to fluctuate dramatically. On very hot, windy days, a corn plant’s water needs can peak at 0.50 inches, which is significantly more than average.
Soil type also plays a major role in how often water must be applied because it dictates the soil’s water-holding capacity. Sandy soils, which retain very little water, will require more frequent but smaller applications to prevent the root zone from drying out. In contrast, clay or fine-textured soils hold water for much longer, allowing for less frequent but deeper watering events.
Visual cues from the plant itself can also signal the need for immediate water application. When a corn plant is experiencing water stress, its leaves will often roll lengthwise into a tight cylinder to reduce the surface area exposed to the sun and conserve moisture. While rolling can occur on hot afternoons even with deep moisture, it signals the plant is struggling and requires an immediate soil check.